Present invention relates to columnar crystals of 6-hydroxy-2-naphthoic acid and process for manufacturing the same.
6-hydroxy-2-naphthoic acid has been employed in manufacturing various industrial products especially dyes, pigments and resins. This compound has usually been manufactured by recrystallizing crude product, which is synthesized by means of the Kolbe-Schmitt reaction, from water or water/alcohol solvent. Thus obtained crystals are in the shape of thin scale with low apparent density, large angle of repose and low fluidity. Therefore, the conventional products have difficulties in handling, especially in transporting, feeding and storing.
The object of the present invention is to provide a process for manufacturing crystalline product of 6-hydroxy-2-naphthoic acid with high apparent density and good fluidity. Due to the present invention, difficulties in handling, especially in transporting, feeding and storing the product can be reduced.
The present invention provides a process for manufacturing columnar crystals of 6-hydroxy-2-naphthoic acid comprising the steps of; dissolving crude 6-hydroxy-2-naphthoic acid in an aqueous solvent, adding crystalline 3-hydroxy-2,7-naphthoic acid as seed crystals to the solution, and cooling the mixture to precipitate columnar crystals.
In another embodiment, the present invention provides a process for manufacturing columnar crystals of 6-hydroxy-2-naphthoic acid comprising the steps of; dissolving crude 6-hydroxy-2-naphthoic acid in an aqueous solvent, adding columnar crystals of 6-hydroxy-2-naphthoic acid as seed crystals to the solution, and cooling the mixture to precipitate columnar crystals.
By virtue of the present invention, manufacturing columnar crystals of 6-hydroxy-2-naphthoic acid was succeeded for the first time. Accordingly, the present invention also provides columnar crystals of 6-hydroxy-2-naphthoic acid having an X-ray diffraction pattern containing peaks (2xcex8) in 16.8-17.8 and/or 21.3-22.3.
The columnar crystals of 6-hydroxy-2-naphthoic acid manufactured by the present process exhibit high apparent density and good fluidity, and therefore, the product of the present invention is far easier in handling, especially in storing, transporting and feeding, than conventional thin scale-form crystals.